<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>AJAX GET请求</title>
    <style>
        #result{
            width: 200px;
            height: 100px;
            border: solid 1px #90b;
        }
    </style>
</head>
<body>
    <button>点击发送请求</button>
    <div id="result"></div>
    <script>
        const btn = document.getElementsByTagName('button')[0];
        const result = document.getElementById('result');
        btn.onclick = function(){
            const xhr = new XMLHttpRequest();
            xhr.open('GET','http://127.0.0.1:8080/server?a=100&b=200');
            xhr.send();
            xhr.onreadystatechange = function(){
                if(xhr.readyState === 4){
                    if(xhr.status >= 200 && xhr.status <=300){
                        //处理结果  行 头 空行 体
                        // console.log(xhr.status)//状态码
                        // console.log(xhr.statusText)//状态字符串
                        // console.log(xhr.getAllResponseHeaders)//所有响应头
                        // console.log(xhr.response)//响应体
                        result.innerHTML = xhr.response;
                    }
                }
            }
        }
    </script>
</body>
</html>